1. Field
Systems and methods for underwater positioning and tracking are disclosed. In particular, an exemplary system provides an acoustic/navigation signal from a transmitter array to an underwater receiver, where the underwater receiver uses the acoustic signal to compute its absolute position.
2. Description of the Related Art
A problem commonly encountered underwater is an inability to accurately determine absolute position. Because high frequency radio waves do not propagate through water, direct reception of GPS or other RF signals, which would otherwise provide good positional information, is not possible. Long baseline positioning systems use multiple transponders that are placed far apart on the seafloor. Their locations must be surveyed after deployment and they must eventually be retrieved, making their use cumbersome and costly. Other systems track pings from underwater units using a receive-only ultra-short baseline (USBL) array, determine the location of the objects, and then transmit locations down to the objects using acoustic modem technology. Such systems have a limit on the number of underwater units that can be tracked by the USBL array, and such underwater units have reduced battery life and increased size because of the power used to transmit to the USBL array.